Frank and Joe Hardy are investigating a mysterious old house high on the cliffs above Barmet Bay when they are frightened off by a mysterious scream. The boys return to the apparently haunted house and make a connection between the place and a smuggling case their father is working on. When their father goes missing, they start-out investigating the secret caves beneath the house but soon confront the smugglers.

Teenage detectives Frank and Joe Hardy investigate a case of counterfeiting.